NATURAL PHILOSOPHY. 115 



A description was then given of the galvanic fuse which has been 

 of late employed for firing guns during their proving trials. It 

 consisted, essentially, of a quill tube, filled with compressed meal pow- 

 der adapted to a wooden head, in which were arranged two small cop- 

 per tubes, with a fine iron wire connecting them, and surrounded with 

 gunpowder. When, therefore, a galvanic current of sufficient power 

 was made to traverse the thin wire, it became heated to redness, and 

 fired the loose powder and the composition in the quill tube, which, 

 being inserted in the vent or touch-hole of the gun, insured the igni- 

 tion of the whole charge. 



Among the inconveniences arising from the application of elec- 

 tricity derived from the voltaic battery were, firstly, the necessity for 

 employing two lengths of wire to complete the circuit, the tedious and 

 difficult operation (in soldiers' hands) of charging the batteries with 

 acid, and the inconvenience and risk of accident attending the trans- 

 port of the necessary agents. 



An extensive series of experiments had been instituted at Wool- 

 wich and Chatham, since 1855, by desire of the Secretary of State for 

 War, by Professor Wheatstone and Mr. Abel, for the purpose of ascer- 

 taining the relative merits of different forms of electricity applied to 

 the explosion of gunpowder. 



The great improvements made in the construction of the induction 

 coil apparatus l}y M. Ruhmkorff, rendered it desirable that experi- 

 ments should be instituted, with small battery power, to obtain the 

 effects of electricity of high tension ; and the results were considered 

 so satisfactory, that Mr. Abel pointed to this form of apparatus as 

 possessing decided advantages for firing a great number of fuses simul- 

 taneously ; in all cases, indeed, when the special nature of the opera- 

 tion would warrant the use of a battery. 



A large magneto-electric apparatus, constructed by Henley, with 

 a lever armature, was the first instrument tried at Woolwich for dis- 

 pensing with the use of the voltaic battery. With this a great number 

 of experiments were made in the endeavor to ignite gunpowder and 

 other compositions of a highly inflammable nature. Little success 

 attended these efforts until moistened gunpowder came eventually to 

 be tried. This exploded, and led to the introduction of Mr. Abel's 

 first " magnet-fuse." In describing its general construction, the lec- 

 turer called attention to the invaluable service rendered in these ex- 

 periments by a particular form of insulated copper wires, manufac- 

 tured according to his instructions, in which two thin wires were 

 separately covered with a non-conducting coating, then laid side by 

 side, and these twin wires further coated and bound up into one by 

 an outer covering of gutta-percha. Whenever a cross-section is made 

 in this the two copper wires are severed, and the terminals brought 

 to view. Short lengths of this material were advantageously ap- 

 plied in the fuse-head, and placed so that the moistened powder rested 

 on the bare terminals. Several hundreds of these quill-fuses were 

 fired with the large lever-magnet with great certainty, the only fail- 

 ures arising from mechanical defects in their manufacture. As a con- 

 venient means of preparing the moist gunpowder in a state fit for 

 priming the fuse, the ordinary fine-grained powder was saturated 

 with a dilute alcoholic solution of chloride of calcium ; on exposure 



